In the field of coating materials these days, coat films have been demanded to have high performance such as, for example, stain resistance. As a method to impart stain resistance to coating materials, a method of adding a hydrolysable silicon compound, especially an organosilicate, to a coating material is known (Patent Document 1). The hydrophilic coat film formed by the method can reduce attachment of oil-based contaminants, and even can allow attached contaminants to be washed out by water droplets such as rain, thereby exerting stain resistance. As an application of the method to water-based coating materials, a method is known in which an organosilicate and a compound (tin compound, phosphoric acid, etc.) to promote hydrolysis and condensation of an alkoxysilane compound are added as a stain resistance-imparting composition to a water-based coating material so that the resulting mixture is used as a stain-resistant water-based coating material (Patent Document 2).
In the above method, however, if the stain resistance-imparting composition is preliminarily mixed with a water-based coating material, hydrolysis of the organosilicate proceeds due to water in the coating material during storage. As a result, gelation occurs, or the reactivity to induce hydrophilic properties is lost, deteriorating the stain resistance. For this reason, the coating material needs to take a two-pack form in which a composition containing the compound to promote hydrolysis and condensation of an alkoxysilane compound is added at the start of coating. Accordingly, the method has some disadvantages such as complex operations and the necessity of an extra container.    Patent Document 1: WO 1994/06870    Patent Document 2: JP-A 2005-15676